The Setup Process
Reminders and the NewsStand.
New Split Keyboard
New Music App
iOS 5 now syncs in the background enabling you to continue work while sycing. Wi-Fi sync is also finally introduced. The updated mail client is even better and Safari is again my standard browser.
Notification Center looks good so far and the tweaks to the Music App are looking great.
Expect more in-depth details and screenshots in the next days.